How do we select the most suited domain or specialization for MS?

Talking about the best-suited specialization, if I have to be honest with you, there is none and there is all. You should choose your specialization entirely on the basis of your interest and future objectives. If you have some interest in the finance field and wish to go ahead in it, you should opt for Finance specialisation. If you feel you are good with handling teams and coming up with strategies, you should go ahead with Marketing and so on. 

So the answer to your question is very subjective.  Let's suppose even if we have a course that is the most demanding one and has the most scope, it is not necessary that it would be relevant to you as well. For instance, if medicine is a course that has the most job opportunities in a specific country and you have no interest whatsoever in the field, it's definitely not the right one for you. I can tell you which place is the most suitable one for which course like the USA is considered best for medical and engineering and the UK is considered the right place for business administration and management, France is known for the fashion field and similarly, various countries have different fields which have the most number of universities and employment opportunities over there. 

 

Why don’t you tell me more about your academic background, extracurriculars, and interests, and maybe then I can find out which course would be the most appropriate for you and which country you can consider for the same.